U.S. patent application number 15/352784 was filed with the patent office on 2017-05-18 for branched diesters and methods of making and using the same.
The applicant listed for this patent is TRENT UNIVERSITY. Invention is credited to Laziz Bouzidi, Suresh Narine, Latchmi Raghunanan.
Application Number | 20170137739 15/352784 |
Document ID | / |
Family ID | 58691414 |
Filed Date | 2017-05-18 |
United States Patent
Application |
20170137739 |
Kind Code |
A1 |
Narine; Suresh ; et
al. |
May 18, 2017 |
BRANCHED DIESTERS AND METHODS OF MAKING AND USING THE SAME
Abstract
The disclosure generally provides branched diester compounds
having exceptional low-temperature and flow properties. The
disclosure also provides uses of the branched diester compounds in
lubricant compositions, for example, as a base oil, and in other
applications where their low-temperature and flow properties can be
employed beneficially. The disclosure also provides efficient and
green methods for making the branched diester compounds. In certain
embodiments, a vegetable oil-based diester (1,6-hexyldioleate) was
branched with propanoic acid (C3) using a green synthetic approach
involving solvent-free and catalyst-free epoxide ring opening
followed by in situ normal esterification. A total of three
branched ester derivatives possessing varied numbers of internal
protruding branched ester groups and hydroxyl groups were obtained.
All of the pure branched derivatives were comprised of mixtures of
positional isomers and/or stereoisomers. Differential scanning
calorimetry (DSC) showed that regardless of the composition
inhomogeneity of each branched derivative, crystallization was
suppressed completely in all of the branched compounds, and they
all demonstrated glass transitions below -65.degree. C. Without
being bound by any theory, it is believed that this unique thermal
behavior is attributed to the internal protruding branched moieties
and hydroxyl groups, which dramatically slowed down mass transfer
starting with the least branched compound (2-branched derivative).
The viscosity of the branched compounds was one order of magnitude
larger than that of the starting di ester due to the increased
branching and increased resistance to flow associated with hydrogen
bonding introduced by the OH groups. Overall, these branched
diesters demonstrated superior low temperature and flow properties
comparable to existing non-sustainable commercial lubricants and
analogous biobased materials which makes them suitable alternatives
for use in lubricant formulations particularly in high performance
industrial gear and bearing lubricants.
Inventors: |
Narine; Suresh;
(Peterborough, CA) ; Bouzidi; Laziz;
(Peterborough, CA) ; Raghunanan; Latchmi;
(Peterborough, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TRENT UNIVERSITY |
Peterborough |
|
CA |
|
|
Family ID: |
58691414 |
Appl. No.: |
15/352784 |
Filed: |
November 16, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62255582 |
Nov 16, 2015 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10M 2207/2835 20130101;
C10M 129/72 20130101; C10N 2030/02 20130101; C10M 2207/30 20130101;
C10M 105/04 20130101; C10N 2040/02 20130101; C10M 101/02 20130101;
C10M 2207/2895 20130101; C07C 69/675 20130101; C10M 2203/003
20130101; C10M 2203/1006 20130101; C10M 105/42 20130101; C10M
2207/289 20130101; C10L 2200/0476 20130101; C10M 129/76 20130101;
C07C 69/67 20130101; C10M 2203/022 20130101; C10L 1/191 20130101;
C07C 69/73 20130101; C10L 2270/026 20130101; C10M 105/40 20130101;
C10M 2205/0285 20130101; C10L 1/1905 20130101; C10L 10/08 20130101;
C10M 2207/283 20130101; C10M 105/38 20130101; C10N 2040/04
20130101; C10N 2030/64 20200501; C10M 2207/301 20130101; C10M
2209/102 20130101; C10M 2207/282 20130101; C10M 2209/1023
20130101 |
International
Class: |
C10M 129/72 20060101
C10M129/72; C10M 105/04 20060101 C10M105/04; C07C 69/67 20060101
C07C069/67; C10L 10/08 20060101 C10L010/08; C10L 1/19 20060101
C10L001/19; C07C 69/73 20060101 C07C069/73; C10M 101/02 20060101
C10M101/02; C10M 129/76 20060101 C10M129/76 |
Claims
1. A compound of formula (I): ##STR00021## wherein: R.sup.1,
R.sup.2, R.sup.3, and R.sup.4 are independently a hydrogen atom or
--C(O)--(C.sub.1-6 alkyl); n.sub.1 and n.sub.5 are independently an
integer from 5 to 13; n.sub.2 and n.sub.4 are independently an
integer from 6 to 13; and n.sub.3 is an integer from 2 to 10.
2. The compound of claim 1, wherein one of R.sup.1, R.sup.2,
R.sup.3 or R.sup.4 is a hydrogen atom.
3. The compound of claim 1, wherein one of R.sup.1 R.sup.3 or
R.sup.4 R.sup.1 is --C(O)--(C.sub.1-6 alkyl).
4. The compound of claim 3, wherein one of R.sup.1, R.sup.2,
R.sup.3 or R.sup.4 is --C(O)--CH.sub.2CH.sub.3.
5. The compound of claim 1, wherein no more than two of R.sup.1,
R.sup.2, R.sup.3, and R.sup.4 are a hydrogen atom.
6. The compound of claim 1, wherein no more than one of R.sup.1,
R.sup.2, R.sup.3 and R.sup.4 are a hydrogen atom.
7. The compound of claim 1, wherein none of R.sup.1, R.sup.2,
R.sup.3, and R.sup.4 is a hydrogen atom.
8. The compound of claim 1, wherein n.sub.3 is 2, 4, 6, 8, or
10.
9. The compound of claim 1, wherein n.sub.2 is 7, 9, 11, or 13.
10. The compound of claims 1, wherein n.sub.4 is 7, 9, 11, or
13.
11. The compound of claim 1, wherein n.sub.1 is 5 or 7.
12. The compound of claim 1, wherein n.sub.5 is 5 or 7.
13. A composition comprising one or more compounds of claim 1.
14. The composition of claim 13, which comprises: a first compound
of formula (I), wherein R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are
--C(O)--(C.sub.1-6 alkyl); a second compound of formula (I),
wherein one of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 is a hydrogen
atom, and the other three of R.sup.1, R.sup.2, R.sup.3, and R.sup.4
are --C(O)--(C.sub.1-6 alkyl); and a third compound of formula (1),
wherein two of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are a
hydrogen atom, and the other two of R.sup.1, R.sup.2, R.sup.3, and
R.sup.4 are --C(O)--(C.sub.1-6 alkyl).
15. The composition of claim 14, which comprises: a first compound
of formula (1), wherein R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are
--C(O)--CH.sub.2CH.sub.3; a second compound of formula (1), wherein
one of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 is a hydrogen atom,
and the other three of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are
--C(O)--CH.sub.2CH.sub.3; and a third compound of formula (1),
wherein two of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are a
hydrogen atom, and the other two of R.sup.1, R.sup.2 R.sup.3, and
R.sup.4 are --C(O)--CH.sub.2CH.sub.3.
16. The composition of claim 15, wherein the composition is a
lubricant composition.
17. The composition of 16, further comprising mineral oil or a
poly(alpha-olefin).
18. The composition of claim 17, wherein the composition is a fuel
composition, such as a biodiesel composition.
19. A method of lubricating a surface, comprising: providing a
first surface and a second surface, which are in physical contact
with each other; and contacting the first surface and the second
surface with a composition of claim 13 at a point where the
surfaces are in physical contact with each other.
20. The method of claim 19, wherein at least one of the first
surface or the second surface is the surface of a gear or bearing.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims the benefit of priority from
U.S. provisional application No. 62/255,582 filed on Nov. 16, 2015,
the contents of which are incorporated herein by reference in their
entirety.
TECHNICAL FIELD
[0002] The disclosure generally provides branched diester compounds
having exceptional low-temperature and flow properties. The
disclosure also provides uses of the branched diester compounds in
lubricant compositions, for example, as a base oil, and in other
applications where their low-temperature and flow properties can be
employed beneficially. The disclosure also provides efficient and
green methods for making the branched di ester compounds.
DESCRIPTION OF RELATED ART
[0003] Lubricants can be used to reduce friction between surfaces
of moving parts and thereby reduce wear and prevent damage to such
surfaces and parts. Lubricants are composed primarily of a base
stock and one or more lubricant additives. In most instances, the
base stock is a relatively high-molecular-weight hydrocarbon. To
make lubricants, such as motor oils, transmission fluids, gear
oils, industrial lubricating oils, metal working oils, and the
like, one can start with a lubricant grade of petroleum oil from a
refinery, or a suitable polymerized petrochemical fluid. Into this
base stock, small amounts of additive chemicals are blended to
improve material properties and performance, such as enhancing
lubricity, inhibiting wear and corrosion of metals, and retarding
damage to the fluid from heat and oxidation. As such, various
additives such as oxidation and corrosion inhibitors, dispersing
agents, high pressure additives, anti-foaming agents, metal
deactivators, and other additives suitable for use in lubricant
formulations, can be added in conventional effective
quantities.
[0004] In some instances, however, it can be undesirable to employ
base stocks composed only of hydrocarbons. This is especially true
in applications where there is a large amount of pressure applied
to moving parts, where such compositions tend to fail, and the
parts become damaged. In such instances, one can use synthetic
esters, which can be used either as a base stock or, in smaller
quantities, as an additive. By comparison with the less expensive,
but environmentally less safe mineral oils, synthetic esters can be
used as base oils in cases where the viscosity or temperature
behavior is expected to be placed under stringent demands. Further,
the increasingly important issues of environmental acceptance and
biodegradability are the drivers behind the desire for alternatives
to mineral oil as a base stock in lubricating applications.
[0005] Examples of synthetic esters include polyol esters and
triglycerides found in natural oils. Of key importance to natural
oil-derived lubricants are physical properties, such as improved
low-temperature properties, improved viscosity at the full range of
operating conditions, improved oxidative stability (meaning removal
of any carbon-carbon double bonds in the case of natural
oil-derived materials), and improved thermal stability.
[0006] One class of ester lubricants includes the glycerol esters
found in various natural oils (e.g., seed oils or vegetable oils),
and derivative synthesized therefrom. Natural oils contain a large
and diverse group of molecules comprised predominantly of
triacylglycerols (TAGs) (>95%) and which possess inherent
biodegradability and lubricity. They are abundant renewable,
non-toxic and non-volatile materials suitable as feedstock for the
development of environmentally adapted materials, including
lubricants, according to the principles of green chemistry. In
2012-2013, for example, the global production of natural oils was
approximately 161 MMT--four times that of the production of the
global lubricants industry--and of which some 50% was from
unsaturated fatty acid-rich oilseed crops (e.g., soybean, canola,
and sunflower oils).
[0007] One of the largest limitation of TAG molecules to their
potential applications in lubricant formulations is poor flow
performance at subzero temperatures. Transforming vegetable oils
into linear aliphatic molecules analogous to well-established
synthetic ester analogues currently available in the marketplace is
one of the approaches employed to mitigate this shortcoming. Such
transformations are facilitated by the conversion of TAGs into
their constituent fatty acids or fatty acid esters via hydrolysis
or esterification, respectively. This approach is advantageous in
that it allows the syntheses of materials which can access a wider
viscosity range and lubricity than native vegetable oils. The low
temperature flow performance of vegetable oil-based materials may
be further improved by increasing unsaturation, introducing
molecular asymmetry via varying ester group and double bond
positions, control of double bond configuration, and with the
introduction of branched groups. Of these, branching has been the
most favored because of the increase in oxidative stability which
accompanies the removal of the unsaturated carbon-carbon double
bonds. Branches can be introduced at the double bond positions via
chemical reactions such as epoxidation, acylation, and
etherification.
[0008] Epoxidation can be used to introduce functional groups onto
an olefin. The mechanism occurs via the concerted addition of a
peracid, generated in situ or prepared in advance, to the weakly
nucleophilic double bond of the olefin. Typical peracids used in
the epoxidation of fatty acid esters and related derivatives
include performic acid, perchlorobenzoic acid and peracetic acid.
According to the principles of green chemistry, performic acid is
preferred as it is the least toxic and least corrosive, Subsequent
ring opening of the epoxide with an appropriate nucleophile, e.g.
fatty acids or alcohols, gives the desired .alpha.-hydroxy branched
derivative.
[0009] Such chemistries have been used in various ways to make
synthetic esters from natural oils that have properties that may
make them more suitable for use as a lubricant than the TAGs
themselves. For example, at the Trent Centre for Biomaterials
Research (TCBR), several series of branched ester derivatives have
been prepared via a green one-pot approach which included the
solvent- and catalyst-free ring opening reaction of ester epoxides
with propanoic acid followed by in situ normal esterification of
the a-hydroxy group. See, for example, U.S. Pat. No. 8,741,822 of
Narine et al., which is incorporated herein by reference, and which
discloses various branched polyester derivatives of linear
lipid-based monoesters and a diacid diester. These compounds
demonstrated a wide range of viscosity and suppression of
crystallization down to -90.degree. C., but were limited by the
positional isomerism of the terminal branched groups, such that the
non-protuberant branches resulted in strong crystallization from
the melt. Further, U.S. Patent Application Publication No.
2015/0247104, of Brekan et al., discloses branched diesters for use
in lubricant formulations, wherein the branched groups are
hydrocarbon branches. Such branched diesters possess excellent
low-temperature performance, but generally have a low viscosity
(e.g., 2.8 to 8.1 cSt at 100.degree. C.).
[0010] Thus, there is a continuing need to develop new synthetic
esters that can simultaneously exhibit higher viscosities and
desirable low-temperature performance.
SUMMARY
[0011] The novel diesters disclosed herein overcome one or more of
these challenges by providing compounds that have high viscosity
and possess exceptional low-temperature performance. In certain
embodiments, the branched groups in the functionally branched
derivatives disclosed herein are internal and, therefore,
protuberant, resulting in suppression of crystallization regardless
of the isomeric inhomogeneity of the derivatives (glass transitions
occurred below -65.degree. C.). Furthermore, in certain
embodiments, the polar ester branches and the presence of OH
groups--a consequence of the synthetic approach used to prepare
these materials--result in a large range of viscosity for the
branched derivatives of this work (162-338 mPas at 40.degree. C.
and 24-36 mPas at 100.degree. C.). In certain embodiments, the
branched derivatives disclosed herein possess inherently improved
oxidative stability due to the removal of the double bonds. The low
temperature performance and viscosity of the functionally branched
diester derivatives make them suitable for use as high performance
lubricants including; but not limited to, industrial gear and
bearing oils.
[0012] In a first aspect, the disclosure provides compounds of
formula (I):
##STR00001##
wherein: R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are independently a
hydrogen atom or --C(O)--(C.sub.1-6 alkyl); n.sub.1 and n.sub.5 are
independently an integer from 5 to 13; n.sub.2 and n.sub.4 are
independently an integer from 6 to 13; and n.sub.3 is an integer
from 2 to 10. In some embodiments, n.sub.r, n2, n.sub.4, and
n.sub.5 are 7, and n.sub.3 is 6. In some further such embodiments,
at least two of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are
--C(O)--(C.sub.1-6 alkyl), such as --C(O)--CH.sub.2CH.sub.3.
[0013] In a second aspect, the disclosure provides compositions
comprising one or more compounds of the first aspect. In some
embodiments, the composition is a lubricant composition, such as a
gear oil. In some other embodiments, the composition is a fuel
composition, such as a biodiesel composition.
[0014] In a third aspect, the disclosure provides methods of
lubricating a surface, comprising: providing a first surface and a
second surface, which are in physical contact with each other; and
contacting the first surface and the second surface with a
composition of the second aspect at a point where the surfaces are
in physical contact with each other.
[0015] In a fourth aspect, the disclosure provides methods of
making branched diester compounds, the method comprising: providing
(i) a short-chain diol, and (ii) an unsaturated fatty acid, or an
ester thereof; reacting the short-chain diol with the unsaturated
fatty acid, or the ester thereof, to form a diester comprising two
unsaturated fatty acid moieties; epoxidizing one or more of the
carbon-carbon double bonds of the unsaturated fatty acid moieties
of the diester to form an epoxidized diester; and reacting the
epoxidized diester with a short-chain carboxylic acid, or an ester
thereof, to form a branched diester.
[0016] Further aspects and embodiments are disclosed in the
Detailed Description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The following drawings are provided for purposes of
illustrating various embodiments of the compounds, compositions,
and methods disclosed herein. The drawings are provided for
illustrative purposes only, and are not intended to describe any
preferred compounds, preferred compositions, or preferred methods,
or to serve as a source of any limitations on the scope of the
claimed inventions.
[0018] FIG. 1 shows an embodiment of certain branched diesters
disclosed herein, wherein R.sup.1, R.sup.2, R.sup.3, and R.sup.4
are independently a hydrogen atom or --C(O)--(C.sub.1-6 alkyl);
n.sub.1 and n.sub.5 are independently an integer from 5 to 13;
n.sub.2 and n.sub.4 are independently an integer from 6 to 13; and
n.sub.3 is an integer from 2 to 10.
[0019] FIG. 2 shows a synthetic scheme corresponding to certain
embodiments of making branched diesters disclosed herein.
[0020] FIG. 3 shows a synthetic scheme corresponding to certain
embodiments of making branched diesters disclosed herein.
[0021] FIG. 4 shows: (a) HPLC curves for certain branched diesters;
(b) the .sup.1H MIR spectrum for the diepoxide; and (c) the .sup.1H
NMR spectrum for the 3-branched diester.
[0022] FIG. 5 shows stereoisomers of the diepoxide,
6-(9,10-epoxyoctadecanoyloxy)hexyl-9,10-epoxyoctadecanoate.
[0023] FIG. 6 shows certain positional- and stereo-isomers of the
2-branched diesters.
[0024] FIG. 7 shows certain positional- and stereo-isomers of the
3-branched diesters.
[0025] FIG. 8 shows stereoisomers of 4-branched diester,
6-((9,10-(dipropanoyloxy)-octadecanoyloxy)hexyl-9,10-(dipropanoyloxy)octa-
decanoate.
[0026] FIG. 9 shows the shear rate-shear stress curves of branched
18-6-18 diesters obtained at (a) 0.degree. C., (b) 25.degree. C.,
and (c) 75.degree. C.; number of branches are reported on each
curve; solid lines are fits to the Hierschel-Bulkley model (d)
Herschel-Bulkley-derived power indices of branched diesters as
functions of temperature; dashed lines are guides for the eyes.
[0027] FIG. 10 shows viscosity versus temperature data of (a)
branched diesters (data recorded at 3.degree. C./min; inset in (a)
is a zoom into the 40-100.degree. C.); (b) and inset in (b)
viscosity of the branched diesters at select temperatures as a
function of number of ester branches (top x-axis) and number of OH
groups (bottom x-axis). The measurement temperature in (b) are
shown in front of each curve. Dashed lines are tentative
exponential fits and serve as guides for the eye.
[0028] FIG. 11 shows the DSC (a) cooling and (b) heating
thermograms, respectively, of the 18-6-18 base diester and its
branched derivatives. (c) Glass transition temperature (T.sub.g)
during cooling ( ) and heating (.box-solid.) as a function of
number of branches and number of hydroxyl groups per molecule. The
crystallization onset (.tangle-solidup.) and melting offset () of
the base unbranched di ester are given for comparison purposes.
DETAILED DESCRIPTION
[0029] The following description recites various aspects and
embodiments of the inventions disclosed herein. No particular
embodiment is intended to define the scope of the invention.
Rather, the embodiments provide non-limiting examples of various
compositions, and methods that are included within the scope of the
claimed inventions. The description is to be read from the
perspective of one of ordinary skill in the art. Therefore,
information that is well known to the ordinarily skilled artisan is
not necessarily included.
Definitions
[0030] The following terms and phrases have the meanings indicated
below, unless otherwise provided herein. This disclosure may employ
other terms and phrases not expressly defined herein. Such other
terms and phrases shall have the meanings that they would possess
within the context of this disclosure to those of ordinary skill in
the art. In some instances, a term or phrase may be defined in the
singular or plural. In such instances, it is understood that any
term in the singular may include its plural counterpart and vice
versa, unless expressly indicated to the contrary.
[0031] As used herein, the singular forms "a," "an," and "the"
include plural referents unless the context clearly dictates
otherwise. For example, reference to "a substituent" encompasses a
single substituent as well as two or more substituents, and the
like.
[0032] As used herein, "for example," "for instance," "such as," or
"including" are meant to introduce examples that further clarify
more general subject matter. Unless otherwise expressly indicated,
such examples are provided only as an aid for understanding
embodiments illustrated in the present disclosure, and are not
meant to be limiting in any fashion. Nor do these phrases indicate
any kind of preference for the disclosed embodiment.
[0033] As used herein, "reaction" and "reacting" refer to the
conversion of a substance into a product, irrespective of reagents
or mechanisms involved.
[0034] The terms "group" or "moiety" refers to a linked collection
of atoms or a single atom within a molecular entity, where a
molecular entity is any constitutionally or isotopically distinct
atom, molecule, ion, ion pair, radical, radical ion, complex,
conformer etc., identifiable as a separately distinguishable
entity.
[0035] As used herein, "mix" or "mixed" or "mixture" refers broadly
to any combining of two or more compositions. The two or more
compositions need not have the same physical state; thus, solids
can be "mixed" with liquids, e.g., to form a slurry, suspension, or
solution. Further, these terms do not require any degree of
homogeneity or uniformity of composition. This, such "mixtures" can
be homogeneous or heterogeneous, or can be uniform or non-uniform.
Further, the terms do not require the use of any particular
equipment to carry out the mixing, such as an industrial mixer.
[0036] As used herein, the term "natural oil" refers to oils
derived from various plants or animal sources. These terms include
natural oil derivatives, unless otherwise indicated. The terms also
include modified plant or animal sources (e.g., genetically
modified plant or animal sources), unless indicated otherwise.
Examples of natural oils include, but are not limited to, vegetable
oils, algae oils, fish oils, animal fats, tall oils, derivatives of
these oils, combinations of any of these oils, and the like.
Representative non-limiting examples of vegetable oils include
rapeseed oil (canola oil), coconut oil, corn oil, cottonseed oil,
olive oil, palm oil, peanut oil, safflower oil, sesame oil, soybean
oil, sunflower oil, linseed oil, palm kernel oil, tung oil,
jatropha oil, mustard seed oil, pennycress oil, camelina oil,
hempseed oil, and castor oil. Representative non-limiting examples
of animal fats include lard, tallow, poultry fat, yellow grease,
and fish oil. Tall oils are by-products of wood pulp manufacture.
In some embodiments, the natural oil or natural oil feedstock
comprises one or more unsaturated glycerides (e.g., unsaturated
triglycerides).
[0037] As used herein, "natural oil derivatives" refers to the
compounds or mixtures of compounds derived from a natural oil using
any one or combination of methods known in the art. Such methods
include but are not limited to saponification, fat splitting,
transesterification, esterification, hydrogenation (partial,
selective, or full), isomerization, oxidation, and reduction.
Representative non-limiting examples of natural oil derivatives
include gums, phospholipids, soapstock, acidulated soapstock,
distillate or distillate sludge, fatty acids and fatty acid alkyl
ester (e.g. non-limiting examples such as 2-ethylhexyl ester),
hydroxy substituted variations thereof of the natural oil. For
example, the natural oil derivative may be a fatty acid methyl
ester ("FAME") derived from the glyceride of the natural oil.
[0038] As used herein, "alkyl" refers to a straight or branched
chain saturated hydrocarbon having 1 to 30 carbon atoms, which may
be optionally substituted, as herein further described, with
multiple degrees of substitution being allowed. Examples of
"alkyl," as used herein, include, but are not limited to, methyl,
ethyl, n-propyl, isopropyl, isobutyl, n-butyl, sec-butyl,
tert-butyl, isopentyl, n-pentyl, neopentyl, n-hexyl, and
2-ethylhexyl. The number carbon atoms in an alkyl group is
represented by the phrase "C.sub.x-y alkyl," which refers to an
alkyl group, as herein defined, containing from x to y, inclusive,
carbon atoms. Thus, "C.sub.1-6 alkyl" represents an alkyl chain
having from 1 to 6 carbon atoms and, for example, includes, but is
not limited to, methyl, ethyl, n-propyl, isopropyl, isobutyl,
n-butyl, sec-butyl, tert-butyl, isopentyl, n-pentyl, neopentyl, and
n-hexyl.
[0039] As used herein, the term "short-chain diol" refers to an
aliphatic alcohol having from 1 to 12 carbon atoms and two or more
OH groups. Non-limiting examples include ethylene glycol, propylene
glycol (1,2 and 1,3), etc. In some embodiments, the short-chain
diol has exactly two OH groups. In some embodiments, the
short-chain diol is saturated and/or acyclic.
[0040] As used herein, the term "unsaturated fatty acid" refers to
a carboxylic acid compound having one or more carbon-carbon double
bonds derived from a natural oil, as defined herein. Non-limiting
examples include oleic acid, linoleic acid, linolenic acid,
etc.
[0041] As used herein, the term "short-chain carboxylic acid"
refers to an aliphatic carboxylic acid having from 2 to 12 carbon
atoms. Non-limiting examples include acetic acid, propanoic acid,
butyric acid, etc. In some embodiments, the short-chain carboxylic
acid is saturated (except for the carbonyl bond of the acid group).
In some embodiments, the short-chain carboxylic acid is
acyclic.
[0042] As used herein, "comprise" or "comprises" or "comprising" or
"comprised of" refer to groups that are open, meaning that the
group can include additional members in addition to those expressly
recited. For example, the phrase, "comprises A" means that A must
be present, but that other members can be present too. The terms
"include," "have," and "composed of" and their grammatical variants
have the same meaning. In contrast, "consist of" or "consists of"
or "consisting of" refer to groups that are closed. For example,
the phrase "consists of A" means that A and only A is present.
[0043] As used herein, "or" is to be given its broadest reasonable
interpretation, and is not to be limited to an either/or
construction. Thus, the phrase "comprising A or B" means that A can
be present and not B, or that B is present and not A, or that A and
B are both present. Further, if A, for example, defines a class
that can have multiple members, e.g., A1 and A2, then one or more
members of the class can be present concurrently.
[0044] As used herein, the various functional groups represented
will be understood to have a point of attachment at the functional
group having the hyphen or dash (-) or an asterisk (*). In other
words, in the case of --CH.sub.2CH.sub.2CH.sub.3, it will be
understood that the point of attachment is the CH.sub.2 group at
the far left. If a group is recited without an asterisk or a dash,
then the attachment point is indicated by the plain and ordinary
meaning of the recited group.
[0045] In some instances herein, organic compounds are described
using the "line structure" methodology, where chemical bonds are
indicated by a line, where the carbon atoms are not expressly
labeled, and where the hydrogen atoms covalently bound to carbon
(or the C--H bonds) are not shown at all. For example, by that
convention, the formula represents n-propane.
[0046] As used herein, multi-atom bivalent species are to be read
from left to right. For example, if the specification or claims
recite A-D-E and D is defined as --OC(O)--, the resulting group
with D replaced is: A-OC(O)-E and not A-C(O)O-E.
[0047] Unless a chemical structure expressly describes a carbon
atom as having a particular stereochemical configuration, the
structure is intended to cover compounds where such a stereocenter
has an R or an S configuration.
[0048] Other terms are defined in other portions of this
description, even though not included in this subsection.
Branched Diester Compounds
[0049] In at least one aspect, the disclosure provides branched
diester compounds formed from a short-chain diol and unsaturated
fatty acids (or esters thereof). In some embodiments, the branched
diester compounds are compounds of formula (1):
##STR00002##
wherein: R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are independently a
hydrogen atom or --C(O)--(C.sub.1-6 alkyl); n.sub.1 and n.sub.5 are
independently an integer from 5 to 13; n.sub.2 and n.sub.4 are
independently an integer from 6 to 13; and n.sub.3 is an integer
from 2 to 10. In some embodiments, n.sub.1, n.sub.2, n.sub.4, and
n.sub.5 are 7, and n.sub.3 is 6. In some further such embodiments,
at least two of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are
--C(O)--(C.sub.1-6 alkyl), such as --C(O)--CH.sub.2CH.sub.3.
[0050] In some embodiments, R.sup.1 is a hydrogen atom. In some
other embodiments, R.sup.1 is a --C(O)--(C.sub.1-6 alkyl) moiety,
such as --C(O)--CH.sub.2CH.sub.3. In some embodiments of any of the
foregoing embodiments, R.sup.2 is a hydrogen atom. In some other
embodiments of any of the foregoing embodiments, R.sup.2 is a
--C(O)--(C.sub.1-6 alkyl) moiety, such as --C(O)--CH.sub.2CH.sub.3.
In some embodiments of any of the foregoing embodiments, R.sup.3 is
a hydrogen atom in some other embodiments of any of the foregoing
embodiments, R.sup.3 is a C(O)--(C.sub.1-6 alkyl) moiety, such as
--C(O)--CH.sub.2CH.sub.3. In some embodiments of any of the
foregoing embodiments, R.sup.4 is a hydrogen atom. In some other
embodiments of any of the foregoing embodiments, R.sup.4 is a
--C(O)--(C.sub.1-6 alkyl) moiety, such as --C(O)--CH.sub.2CH.sub.3.
In some embodiments, one of R.sup.1, R.sup.2, R.sup.3, and R.sup.4
is a hydrogen atom. In some embodiments, one of R.sup.1, R.sup.2,
R.sup.3, and R.sup.4 is --C(O)--(C.sub.1-6 alkyl). In some
embodiments, one of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 is
--C(O)--CH.sub.2CH.sub.3.
[0051] In some of the foregoing embodiments, the compounds can be
fully acylated (i.e., none of R.sup.1, R.sup.2, R.sup.3, and
R.sup.4 is a hydrogen atom) or partially acylated (i.e., one, two,
or three of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are acylated).
In some such embodiments, no more than two of R.sup.1, R.sup.2,
R.sup.3 and R.sup.4 are a hydrogen atom. In some other such
embodiments, no more than one of R.sup.1, R.sup.2, R.sup.3, and
R.sup.4 is a hydrogen atom. In some other such embodiments, none of
R.sup.1, R.sup.2 R.sup.1, and R.sup.4 is a hydrogen atom.
[0052] In some embodiments, exactly two of R.sup.1, R.sup.2,
R.sup.3, and R.sup.4 are acylated and exactly two are a hydrogen
atom. Such compounds may be referred to herein as "two-branched"
diesters. In such embodiments, any two of R.sup.1, R.sup.2,
R.sup.3, and R.sup.4 are acylated. For example, in some
embodiments, R.sup.1 and R.sup.2, or R.sup.1 and R.sup.3, or
R.sup.1 and R.sup.4, or R.sup.2 and R.sup.3, or R.sup.2 and
R.sup.4, or R.sup.3 and R.sup.4, are acylated, while, in each case,
the remaining positions are a hydrogen atom.
[0053] In some embodiments, exactly three of :R.sup.1, R.sup.2,
R.sup.3, and R.sup.4 are acylated and exactly one is a hydrogen
atom. Such compounds may be referred to herein as "three-branched"
diesters. In such embodiments, any three of R.sup.1, R.sup.2,
R.sup.3, and R.sup.4 are acylated. For example, in some
embodiments, R.sup.1, R.sup.2, and R.sup.3, or R.sup.1, R.sup.2,
and R.sup.4, or R.sup.1, R.sup.3, and R.sup.4, or R.sup.2, R.sup.3,
and R.sup.4, are acylated, while, in each case, the remaining
position is a hydrogen atom.
[0054] In some embodiments, all of R.sup.1, R.sup.2, R.sup.3, and
R.sup.4 are acylated and none is a hydrogen atom. Such compounds
may be referred to herein as "four-branched" diesters.
[0055] The value of n.sub.3 depends on the diol used to make the
diester. For example, in some embodiments of any of the foregoing
embodiments, n.sub.3 is 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10. In some
such embodiments, n.sub.3 is 2, 4, 6, 8, or 10. In some further
such embodiments, n.sub.3 is 4, 6, or 8. In some even further such
embodiments, n.sub.3 is 6.
[0056] The values of n.sub.1, n.sub.2, n.sub.4, and n.sub.5 depend
on the nature of the unsaturated fatty acid used to make the
branched diester. In some embodiments of any of the aforementioned
embodiments, n.sub.2 is 6, 7, 8, 9, 10, 11, 12, or 13. In some such
embodiments, n.sub.2 is 7, 9, 11, or 13. In some further such
embodiments, n.sub.2 is 7. in some embodiments of any of the
aforementioned embodiments, n.sub.4 is 6, 7, 8, 9, 10, 11, 12, or
13. In some such embodiments, n.sub.4 is 7, 9, 11, or 13. In some
further such embodiments, n.sub.4 is 7. in some embodiments of any
of the aforementioned embodiments, n.sub.1 is 5, 6, 7, 8, 9, 10,
11, 12, or 13. In some such embodiments, n.sub.1 is 5, 7, 9, or 11.
In some further such embodiments, n.sub.1 is 5 or 7. In some even
further such embodiments, n.sub.1 is 7. In some embodiments of any
of the aforementioned embodiments, n.sub.5 is 5, 6, 7, 8, 9, 10,
11, 12, or 13. In some such embodiments, n.sub.5 is 5, 7, 9, or 11.
In some further such embodiments, n.sub.5 is 5 or 7. In some even
further such embodiments, n.sub.5 is 7.
[0057] The branched diesters disclosed herein can be synthesized by
any suitable means, although some means may be more desirable than
others. Suitable synthetic methodologies are disclosed in the
Examples, below. The claims to the compounds, or to compositions
including the compounds, are not limited in any way by the
synthetic method used to make the compounds.
[0058] In certain aspects, the disclosure provides methods of
making branched diester compounds, the method comprising: providing
(i) a short-chain diol, and (ii) an unsaturated fatty acid, or an
ester thereof reacting the short-chain diol with the unsaturated
fatty acid, or the ester thereof, to form a diester comprising two
unsaturated fatty acid moieties; epoxidizing one or more of the
carbon-carbon double bonds of the unsaturated fatty acid moieties
of the diester to form an epoxidized diester; and reacting the
epoxidized diester with a short-chain carboxylic acid, or an ester
thereof, to form a branched diester.
[0059] Any suitable short-chain diol can be used. In some
embodiments, the short-chain diol is a C.sub.2-10 diol. In some
such embodiments, the short-chain diol is ethylene glycol,
1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol,
1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, or
1,10-decanediol. In some such embodiments, the short-chain diol is
1,6-hexanediol. Further, any suitable unsaturated fatty acid, or
ester thereof, can be used. In some embodiments, the unsaturated
fatty acid, or the ester thereof, is a monounsaturated fatty acid,
or an ester thereof. In some such embodiments, the unsaturated
fatty acid, or the ester thereof, is nervonic acid, erucic acid,
gondoic acid, oleic acid, elaidic acid, palmitoleic acid, or any
esters thereof. In some further such embodiments, the unsaturated
fatty acid is oleic acid, or an ester thereof. In embodiments where
a fatty acid ester is employed, the esters can be any suitable
ester, such as C.sub.1-6 alkyl esters, e.g., methyl esters, ethyl
esters, isopropyl esters, etc. The reaction of the diol with the
unsaturated fatty acid or unsaturated fatty acid ester can be
carried out by any suitable method for making esters.
[0060] The epoxidation can be carried out by any suitable
epoxidation method. In certain embodiments, however, the
epoxidation is carried out by methods describes below in the
section entitled "Preparation of Branched Di esters," which is
incorporated herein by reference.
[0061] In some such embodiments, the epoxide ring is opened by
reacting the epoxidized diester with one or more compounds that
include a short-chain carboxylic acid, or an ester thereof. In some
embodiments, the short-chain carboxylic acid, or the ester thereof
is a C.sub.2-6 carboxylic acid, or an ester thereof. In some
further embodiments, the short-chain carboxylic acid, or the ester
thereof, is propanoic acid, or an ester thereof. In some
embodiments, the ring-opening is carried out using a green
solvent-free method, such that the reacting of the epoxidized
diester is carried out in the substantial absence of an organic
solvent. In this context, the term "substantial absence" means that
the reaction mixture includes no more than 10% by weight, or no
more than 5% by weight, or no more than 3% by weight, or no more
than 1% by weight, of an organic solvent, such as
dichloromethane,
Compositions Including Branched Diesters
[0062] In certain aspects, the disclosure provides various
compositions including branched diester compounds of any of the
foregoing embodiments. Such compositions can include the branched
diester compounds in any suitable quantity. Moreover, the
compositions can include two or more branched diester compounds
having different molecular structures or different isomeric
relationships with respect to each other.
[0063] As noted above, various branched diester compounds can be
classified according to their degree of acylation at R.sup.1,
R.sup.2, R.sup.3, and R.sup.4, according to formula (I), above, A
"two-branched" diester refers to a diester that is acylated exactly
twice; a "three-branched" diester refers to a diester that is
acylated exactly three times; and a "four-branched" diester refers
to a diester that is acylated exactly four times. In certain
embodiments, the compositions include combinations of two-branched,
three-branched, and four-branched diesters.
[0064] For example, in some embodiments, composition includes a
first compound of formula (I), wherein R.sup.1, R.sup.2, R.sup.3,
and R.sup.4 are --C(O)--(C.sub.1-6 alkyl); a second compound of
formula (I), wherein one of R.sup.1, R.sup.2, R.sup.3, and R.sup.4
is a hydrogen atom, and the other three of R.sup.1, R.sup.2,
R.sup.3, and R.sup.4 are [0065] --C(O)--(C.sub.1-6 alkyl); and a
third compound of formula (I), wherein two of R.sup.1,
R.sup.2,R.sup.3, and R.sup.4 are a hydrogen atom, and the other two
of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are --C(O)--(C.sub.1-6
alkyl). In some such embodiments, the composition includes a first
compound of formula (I), wherein R.sup.1, R.sup.2, R.sup.3, and
R.sup.4 are --C(O)--CH.sub.2CH.sub.3; a second compound of formula
(I), wherein one of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 is a
hydrogen atom, and the other three of R.sup.1, R.sup.2, R.sup.3,
and R.sup.4 are --C(O)--CH.sub.2CH.sub.3; and a third compound of
formula (I), wherein two of R.sup.1, R.sup.2, R.sup.3, and R.sup.4
are a hydrogen atom, and the other two of R.sup.1, R.sup.2,
R.sup.3, and R.sup.4 are --C(O)--CH.sub.2CH.sub.3.
[0066] In certain embodiments, the compositions disclosed herein
have certain desirable low-temperature properties. For example, in
some embodiments, the composition has a glas transition temperature
(T.sub.g) of no more than -65.degree. C.
[0067] In certain embodiments, the compositions disclosed herein
have a desirable viscosity at relevant temperatures. For example,
in some embodiments, the viscosity of the composition at 40.degree.
C. is at least 160 cP. In some embodiments, the viscosity of the
composition at 100.degree. C. is at least 24 cP.
[0068] Such compositions can be used in a wide array of
applications, including, but not limited to, lubricant compositions
(e.g., oil for gears or bearings), biodiesel compositions (e.g.,
for suppression of crystallization), and plasticizer compositions
(e.g., for plasticizing PVC or PVB).
[0069] In some embodiments, the compositions are lubricant
compositions, such as a gear oil composition. In some such
embodiments, the lubricant composition is a gear oil, such as a
GL-4 gear oil or a GL-5 gear oil. In some such embodiments, the
branched diesters are blended with one or more other base oils.
Non-limiting examples include, but are not limited to, mineral oil
or a polyalpha-olefin). In some such embodiments, the branched
diester compounds make up from 1 to 70 percent by weight, or from 1
to 50 percent by weight, or from 1 to 30 percent by weight, of the
lubricant composition, based on the total weight of the finished
lubricant composition.
[0070] In some such embodiments, the lubricant composition includes
one or more additives. Such additives include, but are not limited
to, dispersants, detergents, anti-wear agents, antioxidants, metal
deactivators, extreme pressure (EP) additives, viscosity modifiers
such as viscosity index improvers, pour point depressants,
corrosion inhibitors, friction coefficient modifiers, colorants,
antifoam agents, antimisting agents, demulsifiers, organomolybdenum
compounds, and zinc dialkyl dithiophosphates. In some embodiments,
for example, where the lubricant composition is blended to be
suitable for use as a gear oil, the lubricant composition includes
a standard additive package, such as an additive package for a GL-4
or GL-5 gear oil.
[0071] The one or more additives can be used in any suitable amount
in the lubricant composition. The quantity and combination of
additives used can depend on a variety of factors, including, but
not limited to, the properties of the base oil, the properties of
the selected additives, and the desired properties of the resulting
composition. In some embodiments, the one or more additives make up
from 0.1 to 50 weight percent, or from 0.1 to 40 weight percent, or
from 0.1 to 30 weight percent, or from 0.1 to 20 weight percent, or
from 0.1 to 15 weight percent.
[0072] Consistent with the use of the compositions disclosed herein
as lubricant compositions, the compositions can be employed in a
lubrication method. For example, in certain aspects, the disclosure
provides methods of lubricating a surface, comprising: providing a
first surface and a second surface, which are in physical contact
with each other; and contacting the first surface and the second
surface with a composition of any one of foregoing embodiments at a
point where the surfaces are in physical contact with each other.
In some embodiments, at least one of the first surface or the
second surface is the surface of a gear or bearing.
[0073] In some other aspects and embodiments, the composition is a
fuel composition, such as a biodiesel composition. In some such
embodiments, the diester compounds make up from 1 to 20 percent by
weight, or from 1 to 10 percent by weight, or from 1 to 5 percent
by weight, of the fuel composition, based on the total weight of
the fuel composition.
EXAMPLES
[0074] The following examples are provided to illustrate one or
more preferred embodiments of the invention. Numerous variations
can be made to the following examples that lie within the scope of
the claimed inventions.
Materials and Methods
Materials
[0075] Formic acid (88 wt %), hydrogen peroxide solution (30 wt %),
propanoic acid (.gtoreq.98%) and anhydrous sodium sulphate (99.4%)
were purchased from Sigma-Aldrich Co. (USA). Acetone,
dichloromethane (DCM), ethyl acetate, and hexanes were purchased
from ACP Chemical Int, (Montreal, Quebec, Canada). Silica gel
(230-400 mesh) was obtained from Rose Scientific Ltd (AB, Canada).
TLC plates (250 .mu.m) were obtained from Silicycle Chemistry
Division (QC, Canada). All materials were used as purchased unless
otherwise specified.
[0076] The base diester, 6-(oleoyloxy)hexyloleate (18-6-18), used
in the preparation of the branched derivatives was prepared in our
laboratory in high yield from an oleic acid derivative and
1,6-hexanediol. The preparation and properties of 18-6-18 were
reported previously.
Analytical Methods
[0077] Chemical Characterization
[0078] 1H-Nuclear Magnetic Resonance
[0079] 1-Dimensional .sup.1H-NMR was obtained using a Varian VNMR
spectrometer [.upsilon.(1H)=399.75 MHz; Varian Inc., Walnut Creek,
Calif., USA] equipped with a 5-mm PRF auto switchable .sup.1H
probe. Samples were dissolved in approximately 2 mL CDCl.sub.3 and
run at 25.degree. C. over a 30,000 Hz spectral window with a 1
second recycle delay. The spectra were collected over 16 transients
and zero-filled to 32 K complex points.
[0080] Mass Spectroscopy
[0081] Electrospray ionization mass spectrometry (ESI-MS) was
performed on an API 3000 triple quadrupole mass spectrometer (PE
Sciex) equipped with an electron ionspray source (ESI). The ion
source and interface conditions were adjusted as follows: ionspray
voltage (IS)=5500V, nebulising gas (GS1)=8, curtain gas (GS2)=8,
entrance potential (EP)=15 V, focusing potential (FP)=330,
declustering potential (DP)=80 V, and HSID temperature=0.degree. C.
Samples (1 ppm (wt/vol)) were prepared using
chloroform-acetonitrile 10:90(v/v). All samples were injected by
direct infusion at a flow of 10 .mu.L/min. Ion signals were
reconstructed using the Analyst 1.6.2 software package (AB Sciex,
Concord, ON).
[0082] High Performance Liquid Chromatography
[0083] HPLC measurements were carried out on a Waters Alliance
(Milford, Mass.) e2695 HPLC system fitted with a Waters ELSD 2424
evaporative light scattering detector (ELSD). The system included
an inline degasser, a pump, and an auto-sampler. A 150.times.4.6 mm
XBridge C18 column (5 .mu.m average particle size, Waters Limited,
Mississauga, ON) was used in the reversed-phase isocratic mode. The
temperature of the column was maintained at 35.degree. C. The ELSD
nitrogen pressure was set at 25 psi and the nebulizer set to
cooling mode. The drift tube temperature was maintained at
55.degree. C. Gain was set at 500. Samples were prepared by
dissolving in chloroform (1 mg/mL). Samples were run for 30 min at
a flow rate of 0.5 ml/min using a mobile phase of chloroform:
acetonitrile (10:90 v/v). Sample size was 10 .mu.L. Chloroform and
acetonitrile were HPLC grade and obtained from VWR International,
Mississauga, ON. The Waters Empower Version 2 software was used for
data collection and data analysis.
[0084] Physical Characterization
[0085] Differential Scanning Calorimetry (DSC)
[0086] DSC measurements were carried out on a Q200 model (TA
instruments, New Castle, Del., USA) under a nitrogen flow of 50
mL/min, Samples (5.5.+-.1.0 mg) were placed in hermetically sealed
aluminum DSC pans and equilibrated at 70.degree. C. for 5 min to
remove thermal history. The cooling profile was subsequently
obtained by cooling the sample to -90.degree. C. at 3.degree.
C/min, and the heating profile obtained upon heating at 3.degree.
C./min to 70.degree. C. following equilibration at -90.degree. C.
for 5 min. The data were analyzed using the `TA Universal Analysis`
software. The thermal values and uncertainties attached are the
average and standard deviation, respectively, of at least three
runs.
[0087] Rheology
[0088] Flow and viscosity properties of the diesters were measured
on an AR2000ex computer-controlled rheometer (TA instruments) using
a 40-mm 2.degree. steel cone geometry. Temperature control was
achieved by Peltier thermoelectric regulation to better than
0.2.degree. C.
[0089] Flow behavior was determined from shear rate-shear stress
experiments using the steady state procedure. Shear stress was
measured as a function of shear rate between 1-1200 s.sup.-1 at
selected temperatures between 100 and 0.degree. C., inclusive. The
system was allowed to come to equilibrium for 5 minutes before each
measurement. Data points were recorded at 1-minute intervals to
give a total of 50 sample points per experiment. Flow behavior was
modelled using both the Herschel-Bulkley (Eqn. 1) and the Ostwald
(Eqn. 2) equations. The former describes the behavior of fluids
which flow with a yield stress. In the absence of a yield stress,
the Herschel Bulkley model transforms into the Ostwald model, from
which viscosity can be derived:
.tau.=.tau..sup.o+.kappa..gamma..sup.a Eqn. 1
.tau.=.eta..gamma..sup.a Eqn. 2
where .tau.=shear stress in Pa, .kappa.=consistency index,
.eta.=viscosity in Pas, .gamma.=shear rate in s.sup.-1,
.tau..sup.o=yield stress in Pa, and a=flow behavior index. When
a=1, fluids are Newtonian (i.e., viscosity is constant over all
shear), and .kappa.=.eta.. When a<1 and a>1, fluids are shear
thinning and shear thickening, respectively.
[0090] The viscosity versus temperature data were collected using
the constant temperature rate method with a shear rate of 200 s-1.
The samples were quickly heated to 110.degree. C. and equilibrated
at this temperature for 5 minutes then cooled down to 0.degree. C.
at a constant rate of 3.0.degree. C./min. Data points were recorded
at 1.degree. C. intervals to give a total of 110 points per
run.
Preparation of Branched Diesters
[0091] The branched diesters were prepared via a 2-stage reaction
as shown in FIG. 2 as Scheme 1. In the first stage of the reaction,
the unsaturated 18-6-18 base diester was converted into a diepoxide
using in situ-generated peroxy acid. In the second stage of the
reaction, the pure diepoxide was ring-opened with propanoic acid at
temperatures previously optimized for similar compounds to give the
2-, 3-, and 4-branched diester derivatives. Note that although
solvent (dichloromethane) was used in the first stage of this small
scale reaction (i.e., in epoxidation) because of the convenience of
faster reaction times and fewer side products that it presents, the
epoxidation can be performed under solvent free conditions,
particularly on larger scales suitable for industrial applications.
In fact, Narine et al. have already disclosed an optimized
ecofriendly and green solvent free method for the epoxidation of
vegetable oil derivatives that can be easily adapted for the large
scale epoxidation of polyunsaturated linear esters such as those
described in the present disclosure. See U.S. Provisional
Application No. 62/109,441, filed Jan. 29, 2015, and incorporated
herein by reference.
[0092] The branched derivatives were subsequently obtained via a
synthetic scheme that was also ecofriendly and green, incorporating
a one pot solvent-free and catalyst free ring opening of the
diepoxide, followed by in situ normal esterification. In the first
part of this one pot reaction, the reactivity of the ring-strained
epoxide moiety towards acid catalyzed ring opening reactions was
exploited to give the 2-branched diester derivative. Subsequent in
situ condensation reactions between the secondary OH groups formed
upon ring opening and the excess propanoic acid, in addition to the
elevated temperatures which facilitated the evaporation of water
and, thus, the forward reaction, gave the higher branched diester
derivatives (3- and 4-branched).
[0093] Note that in the presence of acids, ring opening of the
epoxide occurs via a nucleophilic substitution mechanism which is
dependent on the degree of substitution of the electrophilic
carbonyl centers; S.sub.N1 occurs at the at the more substituted
center to give the major product, while S.sub.N2 occurs at the less
substituted center to give the major product. In the diester of
this work, all of the epoxy-carbonyl centers were equally
substituted, resulting in nucleophilic attack at both the 9 and 10
positions to give a 1:1 mixture of the 9,10-positional isomers,
which is shown in FIG. 3 as Scheme 2.
Synthesis of Diepoxide
[0094] 6-(Oleoyloxy)hexyloleate (18-6-18) (70 g, 108 mmol) was
weighed into a 500 mL round-bottom flask containing a magnetic
stirrer bar, CH.sub.2Cl.sub.2 (100 mL) and formic acid (34 g, 88%)
were added, and the reaction mixture cooled to 0.degree. C. using
an ice bath. H.sub.2O.sub.2 (54 g, 30%) was added dropwise to this
cooled mixture with constant stirring. The reaction was then
removed to room temperature and allowed to proceed until completed
(as determined by TLC, approx. 5 h). Upon completion, the reaction
mixture was diluted with dichloromethane (100 mL) and washed with
water until neutral (4.times.200 mL) before being dried over
anhydrous sodium sulphate and roto-evaporated to give the crude
epoxide as a white solid. Pure epoxide (>99% purity) was
obtained following column chromatography separation using ethyl
acetate-hexanes (1:20 v/v) as the eluent.
[0095] 6-(9,10-epoxyoctadecanoyloxy)hexyl-9,10-epoxyoctadecanoate,
n6O.sub.2; White solid (48 g, 62%); IR (ATR): 1727 (C.dbd.O)
cm.sup.-1, 846 (cis epoxide) cm.sup.-1; .sup.1H-NMR in CDCl.sub.3
.delta. (ppm): 4.04-4.07 (4, t, O--CH.sub.2--), 2.88-2.92 (4, m,
C--O--CH--), 2.27-2.30 (4, t, O.dbd.CCH.sub.2--), 1.60-1.64 (8, m,
O--CCH.sub.2--, O.dbd.CCCH.sub.2--), 1.46-1.49 (12, m,
O--CCCH.sub.2--, C--O--CCH.sub.2--), 1.27-1.38 (40, m,
C--CH.sub.2--), 0.86-0.89 (6, t, C--CH.sub.3). MS (ESI): calculated
for C.sub.42H.sub.78O.sub.6 679, found m/z 702 ([M+Na].sup.+).
Synthesis of Branched Diesters
[0096] The diepoxide (n6O.sub.2; 5 g, 7.4 mmol) was dissolved in
excess propanoic acid (8 g) in a 100 mL round-bottom flask equipped
with a magnetic stirrer bar. The reaction mixture was heated to
95.degree. C. for the 2-branched diester derivative, and
120.degree. C. for the 3- and 4-branched diester derivatives. The
reaction was allowed to progress to completion (4-5 days as
determined by TLC) with vigorous stirring under an atmosphere of
nitrogen. Upon completion, the reaction mixture was quenched by
pouring into water (50 mL). The organic layer was extracted with
ethyl acetate (3.times.50 mL) and washed with saturated NaHCO.sub.3
(1.times.50 mL) and water again until neutral (3.times.50 mL)
before being dried over anhydrous sodium sulphate and concentrated
on the roto-evaporator to afford the crude products as viscous
orange oils. Pure 2-, 3- and 4-branched diesters (purity 95%) were
isolated as colorless oils following column chromatography
separation using (1:5 v/v), (1:5 v/v) and (1:10 v/v) ethyl
acetate-hexanes as the eluting solvents, respectively.
[0097]
6-((9,10-(dipropanoyloxy)octadecanoyloxy)hexyl-9,10-(dipropanoyloxy-
)-octadecanoate, 4-branched; colourless oil (2.2 g, 32%); .sup.1H
-NMR in CDCl.sub.3 .delta. (ppm): 4.97-4.99 (4, t, O--CHCOR),
4.01-4.04 (4, t, O--CH.sub.2--), 2.29-2.34 (8, m,
O.dbd.CCH.sub.2CH.sub.3), 2.23-2.26 (4, t, O.dbd.CCH.sub.2--),
1.55-1.61 (8, m, O--CCH.sub.2--, O.dbd.CCCH.sub.2--), 1.47 (8, m,
O--CHCH.sub.2--), 1.33- 1.36 (4, m, O--CCCH.sub.2--), 1.22-1.24
(40, m, C--CH.sub.2--), 1.10-1.13 (12, t, O.dbd.CCCH.sub.3),
0.83-0.86 (6, t, C--CH.sub.3). MS (ESI): calculated for
C.sub.54H.sub.98O.sub.12 939, found m/z 957
([M+NH.sub.4].sup.+).
[0098]
6-((9(10)-hydroxy-10(9)-propanoyloxy)octadecanoyloxy)hexyl-9,10-(di-
propanoyloxy)octadecanoate, 3-branched; colourless oil (2.77 g,
43%); .sup.1H-NMR in CDCl.sub.3 .delta. (ppm): 4.98-5.00 (2, t,
O--CHCOR), 4.80-4.83 (1, in, O--CHC(OH)), 4.02-4.05 (4, t,
O--CH.sub.2--), 3.56 (1, m, CH(OH)), 2.29-2.37 (6, m,
O.dbd.CCH.sub.2CH.sub.3), 2.25-2.28 (4, m, O.dbd.CCH.sub.2), 1.69
(b.s., OH), 1.60-1.61 (8, m, O--CCH.sub.2--, O.dbd.CCCH.sub.2--),
1.48 (6, m, O--CHCH.sub.2--), 1.33-1.41 (6, m, O--CCCH.sub.2--,
(HO)CCH.sub.2--), 1.23-1.28 (40, m, C--CH.sub.2--), 1.10-1.16 (9,
m, O.dbd.CCCH.sub.3), 0.84-0.87 (6, t, C--CH.sub.3). MS (ESI):
calculated for C.sub.51H.sub.94O.sub.11 883, found m/z 922
([M+K].sup.+).
[0099]
6-((9(10)-hydroxy-10(9)-propanoyloxy)octadecanoyloxy)hexyl-10(9)-hy-
droxy-9(10)-(propanoyloxy)octadecanoate, 2-branched; colourless oil
(1.2 g, 19%); .sup.1H-NMR in CDCl.sub.3 .delta. (ppm): 4.81-4.84
(2, m, O--CHC(OH)), 4.04-4.06 (4, t, O--CH.sub.2--), 3.56-3.59 (2,
m, CH(OH)), 2.34-2.38 (4, q, O.dbd.CCH.sub.2CH.sub.3), 2.26-2.29
(4, dt, O.dbd.CCH.sub.2--), 1.61-1.63 (8, m, O--CCH.sub.2--,
O.dbd.CCCH.sub.2--), 1.49 (b.s., OH), 1.41-1.46 (4, m,
O--CHCH.sub.2--), 1.34-1.40 (8, in, O--CCCH.sub.2--,
(HO)CCH.sub.2--), 1.25-1.29 (40, in, C--CH.sub.2--), 1.14-1.17 (6,
m, O.dbd.CCCH.sub.3), 0.86-0.88 (6, dt, C--CH.sub.3). MS (ESI):
calculated for C.sub.48H.sub.90O.sub.10 827, found m/z 850
([M+Na].sup.-).
Results and Discussion
Structure Characterization
[0100] All of the branched diesters disclosed herein are novel;
their syntheses and characterization are presented for the first
time. The purity of each of the branched diesters was determined
from the HPLC experiments, and the structures of the diepoxide and
branched diesters were confirmed from .sup.1H-NMR and MS
experiments. The HPLC curves showing the purity of the branched
diesters are presented in FIG. 4a, and representative .sup.1H-NMR
spectra of the diepoxide and the 3-branched diester are given in
FIGS. 4b and 4c, respectively. The full .sup.1H-NMR spectra of all
of the branched diesters are presented in the supporting
information. Note that the purity of each of the branched diester
was higher than 95%.
[0101] In the .sup.1H-NMR spectrum of the diepoxide (FIG. 4b), the
proton chemical shifts at 2.8 ppm and 4.05 ppm (arrows in FIG. 4b)
were characteristic of the C--O--CH epoxide proton and the protons
a to the ester group (OCOCH.sub.2), respectively. These indicated
the formation of the epoxide group and the structural integrity of
the linear diester, respectively. The absence of the chemical shift
at 5.2 ppm indicates that all of the unsaturated moieties were
converted into epoxide groups, while the absence of chemical shifts
at 3.6 and 2.4 ppm, characteristic of the CH--OH and
CH.sub.2--C.dbd.O protons, respectively.sub.; confirmed that no
ring-opened side product(s) was present in the isolated diepoxide.
In the branched diesters, and as shown by the arrows in FIG. 4c for
the 3-branched diester, the proton chemical shifts (.delta.) at
5.00 ppm was characteristic of the branched ester-group (i.e., the
O.dbd.COCH tnethyne proton), while the shift at 4.05 ppm
(O.dbd.COCH.sub.2 methylene protons) confirmed that the linear
ester backbone on the molecules remained intact. Other
characteristic shifts of the branched diesters included the CH--OH
shift at 3.4-3.5 ppm, and the absence of the epoxide proton shift
at 2.8 ppm.
[0102] Epoxidation using performic acid proceeds with retention of
stereochemistry, and introduces chirality at each of the carbon
atoms of the epoxide moiety. Thus, epoxidation of the diepoxide
results in a total of three stereoisomers, as shown in Scheme S.1,
shown on FIG. 5, which, upon ring opening, gives a mixture of
resulting stereoisomers for each of the branched derivatives. The
isomeric inhomogeneity of each branched derivative was further
exacerbated by the positional isomerism which occurs upon ring
opening. Thus, 2-branched diesters will have comprised of a total
of ten isomers which possessed both positional and stereo-isomerism
(Scheme S.2, FIG. 6). In the higher branched derivatives, the
number of positional isomers decreased with increasing
esterification OH group such that the 3-branched derivative
comprised of eight isomers possessing both positional and
stereoisomerism (Scheme S.3, FIG. 7), and the 4-branched derivative
comprised of three isomers which possessed only stereoisomerism
(Scheme S.4, FIG. 8). Due to their similar polarities, these
combinations of isomers were not readily separable with the
chromatographic methods readily accessible in our labs
(reversed-phase HPLC or gravity chromatography). Thus, their
separation was not pursued in light of the anticipated difficulty
and high cost of such purifications if used at commercial scales.
Note that the proton chemical shifts of stereoisomers are similar
to each other.
Flow Behavior
[0103] The shear rate-shear stress curves obtained for the branched
diesters at select temperatures (0, 25, 75.degree. C.) are
presented in FIG. 9a-c. All of the branched diesters were well
fitted to the Herschel-Bulkley model (solid lines, FIG. 9a-c;
R2>0.9985) with yield stress values of less than 0.055.+-.0.020
Pas. The power law values derived from these fits are presented in
FIG. 9d as a function of temperature for each diester.
[0104] FIG. 9d shows that the flow behavior of the branched
diesters was shear thinning at low temperatures
(0.80.ltoreq.a<0.99 from -5 to 40.degree. C.), progressing
exponentially with increasing temperature (characteristic
temperature 11.0.+-.1.4.degree. C., R.sup.2.gtoreq.0.9735) towards
Newtonian. As can be seen in FIG. 9d, at any given temperature in
the shear thinning region, the power index of the 2-branched
diester was less than that of the 3-branched diester, which in turn
was less than the 4-branched diester. That is, the branched diester
derivatives were increasingly shear thinning with increasing number
of OH groups and corresponding decreasing numbers of protuberant
branched groups. Note that at the same temperatures, the difference
between the power indexes of the 3- and 4-branched diesters was
markedly smaller compared to the difference between the 2- and
3-branched diesters, indicating the prevailing effect of hydrogen
bonding. Similar shear thinning flow behaviour
(0.76.ltoreq.a<0.99 for temperatures from -5 to 55.degree. C.)
have also been reported for branched diacid-derived jojoba-like
diesters. The branched diacid-derived diesters were also
increasingly shear thinning with increasing numbers of OH groups
and decreasing branching.
[0105] These results may be understood in terms of the total
intermolecular interactions and mass transfer limitation
considerations. Shear thinning occurs when the stress which
dominates at low shear rates does not increase with shear rate as
fast as the Newtonian viscous stress.
[0106] This stress is the result of the weak intermolecular
interactions which exists between the branched diesters. It is
greatest in the 2-branched diesters because this compound has the
most hydrogen bonding density. At higher shear rates, poor mass
transfer limits the reformation of these intermolecular bonds which
break with shearing.
Viscosity
[0107] FIG. 10a shows the viscosity-temperature data of the
branched derivatives of 18-6-18 diester. The viscosity of the
branched diesters were all an order of magnitude higher than that
of the unbranched 18-6-18 base diester (which spanned 0.006 to 0.5
Pas from 100 to 0.degree. C.), outlining the dramatic effect of
hydrogen bond density, mass and steric geometric hindrance
(bulkiness) associated with the introduction of the branched ester
groups. Amongst the branched diesters, increasing hydrogen bonding
was clearly the dominating factor influencing viscosity. At any
given temperature, the viscosity of the 2-branched di ester was
larger than that of the 3-branched diester, which in turn was
greater than that of the 4-branched diester, a result directly
linked to the number of hydroxyl groups of the branched derivatives
(zero, one and two OH groups in the in the 4-, 3- and 2 branched
diesters, respectively). This data indicate that the effect on the
viscosity of hydrogen bonding density is measurable and
significant.
[0108] This is further clarified in FIG. 10b which show the
viscosity at example temperatures reported as a function of the
number of branched groups and the number of OH groups. The
seemingly exponential trends (R.sup.2.gtoreq.0.9525) of FIG. 10b is
similar to what was observed for branched diacid-derived diesters
with non-terminal OH groups, or alternately, possessing terminal
acyl groups, confirming the predominant effect of hydrogen bond
density over the small ester group.
Thermal Transition Behavior
[0109] The thermal transition behavior of the branched 18-6-18 are
presented in FIG. 11; FIG. 11a and FIG. 11b show the cooling and
heating thermograms, respectively, and FIG. 11c present the
characteristic temperatures versus the number of branched groups
and hydroxyl groups. The cooling and heating thermograms and
characteristic crystallization and melting temperatures of the
unbranched base diester, 18-6-18 are also presented for comparison
purposes.
[0110] FIG. 11a-b show that the thermal behavior of all the
branched diesters was fundamentally different from that of the
unbranched 18-6-18 diester. The unbranched diester crystallized
with a sharp peak with an onset at 2.2.+-.0.6.degree. C. and a
total enthalpy of 104.6.+-.4.2 kJ/mol. These DSC characteristics of
the 18-6-18 unbranched diester were previously shown to be those of
the crystal phase having the triclinic subcell structure (so-called
.beta.-form). The thermograms of the branched diesters, on the
other hand, showed only a glass transition which occurred at more
than 60.degree. C. below the crystallization temperature of the
unbranched diester. The heating profiles of the branched diesters
mirrored their cooling counterparts with a simple transformation
from the glass to the liquid phase, and with no crystallization
mediated by melt a desirable behavior in materials for use in
lubricant formulations.
[0111] The crystallization was completely suppressed in these
internally-branched diesters in contrast to analogous diesters
whose branched ester groups (also three carbons long) were terminal
and in which crystallization was not fully suppressed and/or strong
crystallization mediated by melt occurred upon heating. This
indicates that the steric hindrance due to the protuberant ester
branch on the fatty acid moiety was highly effective in disrupting
the ability of the branched diester molecules to pack regularly in
a crystal form. It is also likely that the difficulty of the
branched molecules to pack was further exacerbated by the
compositional inhomogeneity within each branched system due to the
presence of positional- and/or stereo-isomers.
[0112] These results also contrast with those of analogous
internally-branched monoesters--with similar total carbon chain
length (44 C) and similar branched groups (propyl esters)--in which
crystallization was not fully suppressed and/or in which
recrystallization from the melt was promoted by the hydrogen
bonding present in the 2- and 3-branched derivatives. This
indicated that the second `extra` ester group along the aliphatic
backbone of the molecule introduced enough steric hindrance or
"bulkiness" to suppress the crystallization completely. Note that
similar steric hindrance between the aliphatic chain moieties of
unbranched esters also accounts for the difference of
.about.15.degree. C. in the crystallization temperature of the
unbranched jojoba-like diester compared to unbranched jojoba-like
monoester with similar chain length.
[0113] FIG. 11c shows that the glass transition of the 2-branched
diester which has two OH groups occurred at the highest temperature
(T.sub.g=-60.5.+-.0.3.degree. C.). The addition of a branch--and
the associated removal of an OH group--to give the 3-branched
diester resulted in a decrease in T.sub.g by 12.degree. C.
(T.sub.g=-72.9.+-.0.5.degree. C.). Generally, T.sub.g increases
with increasing viscosity. As was shown in the preceding section,
the viscosity of the branched diesters increased exponentially with
increasing hydrogen bond density, indicating that the reduction in
T.sub.g with increasing branching was primarily due to decreased
viscosity (338 mPas versus 162 mPas at 40.degree. C. for 2- and
3-branched diesters, respectively) associated with reduction of
hydrogen bond density. Similar decreases in T.sub.g with decreasing
OH content have been reported for branched jojoba-like monoesters
and diesters. In the 4-branched diester of this disclosure, the
addition of the fourth group, and the associated removal of the
last OH group (and therefore all hydrogen bonding), resulted in a
small 2.degree. C.) increase in the glass transition temperature
(T.sub.g=-69.5.+-.0.5.degree. C.) compared to the 3-branched
diester. This indicates that in the absence of hydrogen bonding,
mass transfer limitations due to increasing molecular
mass/molecular bulkiness also contributes significantly towards the
viscosity, and hence, T.sub.g, of these branched diesters.
[0114] T.sub.g was determined by the competing influence of
decreased OH content and mass transfer limitations which accompany
increased branching. The crystallization was effectively suppressed
due the combined influence of internal protuberant groups upon
branching, and the intermolecular steric hindrance upon the
introduction of additional ester groups along the linear backbone
of the molecule (e.g. linear monoesters versus linear diesters)
which affects the close packing of the linear aliphatic chain
segments of individual ester molecules. Note that the latter alone
was not sufficient to effectively suppress crystallization.
Implications
[0115] The flow properties of the branched diesters of this work
are presented in Table 1 (below) alongside those of typical
commercial lubricants (mineral oil, polyalphaolefin, isoalkyl
adipate) and the best-performing representative bio-based
lubricants from the literature. Polyalphaolefins (PAO) and isoalkyl
adipates (e.g. di i-C13 adipate) are examples of synthetic
biodegradable basestocks. The flow properties of a soybean oil
basestock have also been included for comparison. JLEM and JLED in
Table 1 refer to the jojoba-like mono- and diesters, respectively,
reported by the TCBR research group.
[0116] Table 1 shows that of the commercial lubricating basestocks,
polyalphaolefin (PAO) maintained its fluidity at the lowest
temperature (-63.degree. C.), but also had the lowest viscosity (17
cP at 40.degree. C.). The pour points (PP) reported for the
best-performing biobased alternatives in the literature are
comparable to that of PAO, but the viscosity is higher overall,
ranging from .about.30 cP--two times that of PAO--to .about.390 cP
at 40.degree. C. The increased number of ester groups and hydrogen
bonding density where OH groups were introduced was responsible for
the higher viscosity of the biobased polyesters compared to PAO.
The latter possessed only the relatively weaker van der Waals
interactions arising from its hydrocarbon-only structure. Note also
that all of the compounds presented in Table 1, including the best
low temperature performance alternatives found in the literature,
possess a combination of the structural elements known to influence
crystallization, namely: kinks along the aliphatic backbone such as
ester groups or cis-double bonds, and branched chains close to the
ends of the molecules and/or within the molecule.
[0117] Of the biobased polyesters listed in Table 1, all of the
fully branched derivatives of the jojoba-like monoesters (JLEM) and
jojoba-like diesters (JLED) with internal ester branches did not
crystallize and presented glass transitions below -57.degree. C.
instead. The presence of OH groups alongside ester groups at the
terminal position, such as in the case of the partial branching
(i.e., 2- and 3-branched) of JLEMs with terminal double bonds (e.g.
entries 10-11 in Table 1), was demonstrated to suppress
crystallization effectively when the OH was terminal and the
branched ester group was protuberant. In order to take advantage of
the derivatives of partial branching of JLEMs having terminal
double bonds for low temperature performance lubricants, it would
be necessary to isolate the effective positional isomer from the
mixtures--a not so easy nor economical task at commercial scales.
Even then, as has been clearly demonstrated, the desired positional
isomers experience, over time, intramolecular 1,2-acyl group
migration in which the ester group switches position with the
terminal OH groups forming a more stable but much less effective
isomer(s) which experience lingering crystallization during cooling
and/or strong recrystallizations mediated by melt upon heating. In
contrast, the branching of the diester of this work, although
resulting in mixtures of different isomers, was very effective in
suppressing crystallization, including with partial branching (the
2- and 3-branched derivatives). This is because all of the branches
were internal, and an intramolecular 1,2-acyl group migration, if
any, would not affect the protuberant nature of the branches and,
therefore, would not impact the thermal behavior of the mixture
significantly. It is therefore likely that there would be no need
to separate the positional isomers to keep the low temperature
performance of the mixtures.
[0118] The viscosity of the jojoba-like branched mono- and
di-esters, inclusive of the branched diesters of this work,
presented in Table 1 extended from 43 cP to .about.340 cP (at
40.degree. C.) depending on the total chain length, number and
position of OH groups present. This viscosity range is markedly
larger than what was reported for the other biobased compounds
listed in Table 1, including the branched diesters of the present
work (162-338 cP at 40.degree. C.). Table 1 also shows that the
branched jojoba-like esters, even if they present similar low
temperature performance (i.e., same T.sub.g) as the branched
derivatives of the present work, may present widely different
viscosity. For example, the 2-branched 18-6-18 (entry 17 in Table
1) and the 2-branched JLEMs with 28 carbon atoms (entry 10 in Table
1) present similar T.sub.g (-64.degree. C.), but viscosities of 338
cP and 290 cP at 40.degree. C., respectively. This does not
preclude the use of these branched JLEMs and JLEDs, including the
branched diesters of this work, in dedicated different low
temperature applications based on their different viscosity
classifications. For example, based on ISO specifications (ISO
3448: 1992) (and assuming that the dynamic viscosity for the
branched diesters of this work can be acceptably compared to
kinematic viscosity), the 2-branched, 3-branched and 4-branched
18-6-18 diesters may be classified as ISO VG 320, ISO VG 220, and
ISO VG 150 industry oil grades, respectively, for use in industrial
gear and bearing lubricants.
[0119] These results indicate that crystallization in the linear
aliphatic diesters of the 18-n-18 series with varying diol chain
lengths, which all possess internal double bonds, may be similarly
suppressed upon the introduction of internal protuberant branched
ester groups.
[0120] The thermal and rheology results show that the branched
18-6-18 diesters of this work can be used in lubricant formulations
with improved low temperature performance compared to present
commercial alternatives, inclusive of biobased alternatives. Like
the branched JLEMs and JLEDs previously reported by our research
group, the branched 18-6-18 diesters of the present work can be
prepared using solvent free and catalyst free chemistries. The
absence of double bonds in these compounds is also expected to
result in improved oxidative stability compared to the branched
alternatives which contain carbon-carbon unsaturation such as, for
example, entry 8 in Table 1, The branched derivatives of 18-6-18
diester also improve on the branched JLEMs and JLED reported
previously by our research group in that they can be used to
formulate lubricants with similar low temperature properties and
more varied viscosity profiles. Furthermore, the diesters of this
work show increased potential for use as low temperature
alternatives without the need for the separation of the isomers or
without concern for the effects of the acyl group migration between
the .alpha.-OH and ester groups in the partially branched
derivatives upon storage or during thermal processing.
TABLE-US-00001 TABLE 1 Vis- Total cos- chain ity, length.sup.a Pour
cP @ (car- Point.sup.b, 40.degree. Entry Material bons) Structure
.degree. C. C. 1 Mineral -21 71.sup.c Oil.sup.d 2 PAO.sup.d
##STR00003## -63 17.sup.c 3 Soybean Oil.sup.d 39 ##STR00004## -9
32.sup.c 4 Di i-C13 adipate.sup.d 32 ##STR00005## -54 27.sup.c 5
Estolide.sup.e 31 ##STR00006## -45 47.sup.c 6 Diester.sup.f 35
##STR00007## -60 290 7 Triester.sup.g 35 ##STR00008## -62 -- 8
Diester.sup.h 46 ##STR00009## -62 137.sup.c 9 JLEM.sup.i 26
##STR00010## <-90.degree. C. 43 10 JLEM.sup.i 28 ##STR00011##
-64 (T.sub.g) 290 11 JLEM.sup.i 28 ##STR00012## -63 (T.sub.g) 232
12 JLEM.sup.i 31 ##STR00013## -77 (T.sub.g) 84 13 JLEM.sup.i 31
##STR00014## -85 (T.sub.g) 66 14 JLEM.sup.j 36 ##STR00015## -57
(T.sub.g) 391 15 JLEM.sup.j 36 ##STR00016## -73 (T.sub.g) 130 16
JLED.sup.k 44 ##STR00017## -72 (T.sub.g) 210 17 JLED (this
disclosure) 42 ##STR00018## -64 (T.sub.g) 338 18 JLED (this
disclosure) 42 ##STR00019## -77 (T.sub.g) 211 19 JLED (this
disclosure) 42 ##STR00020## -73 (T.sub.g) 162
[0121] In Table 1, the superscripts correspond to the following
information. (a) Number of carbon atoms contained in the longest
linear segment. (b) ASTM derived value for the last temperature at
which a liquid will flow. (c) Dynamic viscosity was calculated from
Kinematic viscosity using the relationship: Dynamic viscosity
(cP)=Kinematic viscosity (cSt).times.Density (g/cm.sup.3), and
assuming that density=1 g/cm.sup.3. (d) As reported in literature.
p (e) As reported in literature. (f) As reported in literature. (g)
As reported in literature. (h) As reported in literature. (i)
Jojoba-like branched monoester. (j) Jojoba-like branched monoester.
(k) Jojoba-like branched diester.
Conclusions
[0122] Novel aliphatic polyesters containing 2-, 3-, and 4-short
chain (3-carbon) ester branches have been synthesized from
6-(oleoyloxy)hexyloleate (18-6-18) using a green ecofriendly
approach which incorporated solvent-free and catalyst-free one pot
chemistries. The viscosity of the base material increased by an
order of magnitude upon branching due to the combined effects of
increased mass, and integrated steric hindrances and hydrogen
bonding. The internal nature of the sites of functionalization by
enabling protruding ester branches and OH groups in the branched
derivatives proved to be a structural feature that is instrumental
in the resulting suppression of the crystallization independently
of the degree of branching. The effectiveness of such branching was
reflected in single glass transitions that appeared at very low
temperatures, between -64.degree. C. and -77.degree. C. on both
cooling and heating. The T.sub.g which is akin to the pour point
depended on the number of branches and hydroxyl groups. The effect
of hydrogen bond density on the viscosity was not only significant
and measurable but also readily predictable as it scaled
exponentially with the number of OH group at all temperatures in
the liquid state.
[0123] The low temperature performance and viscosity profiles were
obtained with mixtures comprising positional- and/or
stereo-isomers. In fact there is no need for the separation of the
isomers of the branched derivatives of 18-6-18 to obtain the
desired excellent performance contrary to analogous previously
studied derivatives of esters with terminal functionality, where a
terminal position of the ester group in partially branched
derivatives resulted in very poor performance of the material.
Furthermore, the possible migration of the acyl chain which
switches position with the OH group upon storage would not alter
the phase trajectories in the partially branched derivatives of
18-6-18 as it did in their counterparts with terminal
functionality.
[0124] Overall, the branched diesters of this disclosure presented
thermal transition and viscosity profiles which are superior to
existing analogous bio-based materials, making them suitable as
green alternatives for high performance lubricant formulations.
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